Current limit generator



MarCh 20, 1951 A. w. KIMBALI. ET AL 2,546,003

CURRENT LIMIT GENERATOR Filed Feb. 28, 1948 2 Sheets-Sheet 1 ,q A /5-a H) di;

' 0 Q 50 'e3 /o E5 c UUU ({72 70 f1' .Z x' 9 y 3 l R 0 ATTORNEY March 20, 1951 A, w, KlMBALL ETAL 2,546,003

CURRENT LIMIT GENERATOR Filed Feb; 28, 1948 2 Sheets-Sheet 2 A 37 37 /Cjg'r 3 M) l! el/7 Z5 QQ L6 /7 ,/f/ 36 ATTORNEY Patented Mar. 20, 1951 UNITED STATES PATENT OFFICE CURRENT LIDHT GENERATOR Application February 28, 1948, Serial No. 11,908

16 Claims.

Our invention relates to electric machines, particularly in connection with drives of the Ward Leonard or variable voltage type.

The control system of such a drive includes a generator whose armature output circuit feeds energizing current of variable voltage to the drive motor to be controlled, while the generator field is supplied With regulatable excitation from a controlled current source which may consist of another generator so as to form a cascade arrangement of dependently operating generators.

In control systems of the general type just described, it is often desirable to impose certain limitations on the output current or voltage applied to the machine to be ultimately controlled or supplied by one of the generators of one or more of the following generators of the cascade arrangement. This will best be understood from an example:

In mine hoist drives, reversing blooming mills and other similar equipment where heavy masses are to be accelerated, it is desirable to limit the peak currents acting on the motor, in order to prevent damage to the motor and the equipment driven thereby. The torque of the hoist motor and, consequently, the stress on the ropes and other mechanical parts are a function of the motor current. Therefore, limiting the current to a maximum value will, in turn, keep the mechanical stress at a safe value. The hoist motor and its associated generator are designed to commutate certain maximum currents. Sparking at the brushes will be excessive when these currents are exceeded, and more than normal maintenance will then be required to keep the commutator functioning properly. Hence, a limitation of the maximum current will reduce the maintenance cost on the main equipment and afford the application of equipment with smaller margins of overload rating.

While attempts have heretofore been made to solve the difnculties and with some measure of success, such previous designs had some serious limitations. Due to the physical construction of the current limitgenerator, there was no space for commutating poles, and thus the armature load current was limited by the commutating ability of the machine without commutating poles. Further, the resultant saturation curve of this generator differed from the one theory dictated. The generator also would not operate on a saturating curve that remains at zero for a certain rise in motor load current and then rise as he motor load current increased some more.

The cause of most excessive current in mine may lead to other drawbacks incident to the interruption of the operating current.

These conditions, while elucidated by the example of mine hoists, obtain also in other kinds of cascade-connected generator systems for variable voltage control. v I

It is an object of our invention to provide control systems of the type here in point which afford an automatic current limitation without the use of circuit breakers, or the like interrupting devices, in the control system proper.

According to another object, the invention aims at providing a cascade-connected generator' arrangement for variable voltage control in which a current-limiting effect is produced by one of these generators.

It is also an object to provide an electric machine, such as a generator, whose characteristic of operation affords a limiting eifect so as to be applicable in systems and for the purpose just mentioned.

Another object of our invention is to provide a reversible current-limiting drive control in accordance with the foregoing aims that permits an asymmetric operation, i. e., a shifting of the limit conditions in dependence upon the direction of a control function, in particular when applying the control system to hoist drives.

In order to achieve the above-mentioned objects and advantages, the invention, in one of its aspects, consists in a variable voltage control system designed and functioning inthe following manner: A main generator with an armature circuit for supplying the variable voltage to be controlled has its field circuit connected to the armature output circuit of a regulating generator, either directly or over an intermediate cascadeconnected generator, whose field circuit is energized in dependence upon the current to be controlled and inductively associated with saturable magnetic means for biasing the energization of the main generator eld due to saturation of the magnetic means when the current exceeds a given limit value so as to produce the desired current or voltage limiting effect.

In another aspect, allied to the foregoing and more specific, the invention provides for the direct or indirect control of the main generator a regulating generator whose eld poles include magnetic shunt means which become saturated when the appertaining field current, in dependence upon the current to he controlled, exceeds a given value.;l

Other objects, advantages, andffeatures of the invention will be apparent from the description,

presented hereinafter, of the embodiment illus--l0 trated in the drawings, in which:

Figure 1 exemplifies the invention yloyshovving a circuit diagram of a control/systernvforfa miner hoist drive, and

Fig. 2 is an explanatory diagramrelating to-l5 the saturation characteristic of a current-regn---i lating generator which forms .part of.;thewconi-i trol system of Fig. l, while Figs. 3 and 4 represent cross-sectionalzviews .offl a machine built in accordance with our teachingsg-togprovideethe required saturation, charac-ffv oandzfto :beg used-1 as i a currentfre,.sulating`l` mfthecontrol. system of `Fie 1. gf-to lthe, hoistfcontrolzsystern shown in- Vhe hoisting equipment properis ,schemati- 'Y l5 cally-qindicatedfat-v-,l and' includes -a'fhoisting drum Whoseggshaft-QZ fislmechanicallyconnected to the armatnredof; adriying motor-HM; Theiield WindiIlgS- rOf: IIlOQI' im: S'fenergiZed from pa separatejcurrent source of substantially. constant :3 0

voltage, and tothi s;;end;;is1connected through leads E13-fand54withfjangexciter generatorxidenoted by-:EX The 1connection-,f.irlcluflcs an` adjusting@L rhecstatxlthc. Oncezrrcnerlyadi, ,.ftherneo.= stat RI need not be variedr., operaticnrofethesfcfzntrcl systemf Ihevarrnature l il -`fofythe `hoist motor is.,A connectedgtoz a; feed circuit; A I l in series arrangement tQvtheLarrnature 2m of; agmain'- generator MG which formsgtheA-currentfsourcerof the feed 40.

circuit Alf.; The maingenerator MG has aimain field; WindA i g2 liconnected, to a -control circuit A2givhosemurrentrsourceis formed-by thearrna.- ture Basora controlvgenerator CG; A resistor-R2 Y uriner the.

is series-arranged in circuit A2,'.Nilmeral122xsi denctesfal-.comnensatins-rorffinterpclelwinding .of the main: generator MG..

The.; control, generator CG hasvite eldwind ings,-;1numberedf;;3l throughk 35,.- inrordergtofcon-Y trol the voltage impressed on the main generator eld-:xwindingg 2|; Consequentlw the: resultant encrgizationfnf; Iield.:wirriing52'If-dcnencis'von'v the interaction fof-:the ve iield windings-of v the icon,- trolgenerator CG fand .determinesgthevoltage andcurrentsuppliedgby the v'mai-n; vgenerator armature l5s zthroughgltheifeed circuiti AiV to the hoist. motor HM, thereby controlling @the 'torqueforspeed oftheahoistingequipment driven lby t,the-motor Thezfarmaturepoutput, currentf ing;V circuit AZ-is;

whichytherefore, is designated inv theifollowing; asv'thesprincipaL-or pattern, .field winding :oi-the. controlgenerator'CG'. The self-,energiZingelda winding 32. servestoi.v amplify the control effect andlisL-connected. fingthe Afcircuit'fAZ.; While ,-thisj 65 connection*fisrshown-as afseries arrangement, aY selfenergizingshunt windingr-may--be usedffiinstead.- `Considering-the eld ofiwinding'St asa reference-and: assuming thatv the.. generator supplied 'energyzfto .the hoist motor. rather than 7G functioning-.fin 1a.- ;regenerative sense,.\.windings 32: andE 135, vfact:ecuxnulativelythatv is :their i ampere.,

turnszzarefinna.proper directionA to;l assist,` the g' ampere turns of field winding 3L Injl contrastvv theretothe.- twoe field: windingsc' 3;. andgnc act differentially with regard to Winding 3l. It should be noted that for certain Values of current in circuit Al, as explained later, eld winding 33 will be substantially deenergized. However, as long as it is energized due to the action of generator RG, the eiect of its ampere turns willA subtract fromfthat off'etheampere turns of winding 3|.l In other words,.;.the currentgefective in the differential eld windings 33 and 34 ftencls to diminish the resultant field strength genera-tor CC-i. serves tol. :compensateior the JR;

drop in the armature.` circuit .of the, hoist motor, and is connected across f winding.V 221.-. through leads r23 and-26 Vfand-:in series with a. calibrating.,

resistor .R3 f.

The pattern Iield winding .3 I.-, serving. to ldeter-r minefthe basic-speed. ofV the4 hoist.. motor; as .to direction Vand Qmagnitude, isr energized from .,a.,

currentssourceeof constant voltage under,..con

trolby,A operatorfactuated;voltage. regulating. and.`

reversing vmeans.rv`v More', in detail, pattern .windingggtisA connected throughmains. 53 .and .ill...to.. ;v the...,exciterAv a;- -reversing switclrRS.A being ternosedin ordcr,. to.;select; thepolarity-,oi the pattern...voltage ;v impressed.; on field winding. .3 I

The connection includesaa contr-.oldev-ice.. CO; which-hasaresistor R8,,connectedebetweenmain 53 and reversing switch RS.

TheY reversing switch. lRSas illustrated/,has two movablecontacts @mand-,10, .each cooperatingfwith two-stationary ,contactslcand 62V, and-v 1 l .and.12,. respectively.. Inonepositionof switch.V

RS, .-contact. Se fis .in engagementwitncontact .61.,

land -contactmiwith ,contact 1 I,in order to.ener gize-,the hoist. motonHM for'. operation inthe.. hoisting-direction... In .its .othera position, theA reversing.v switch RS: connects .movable i contacts..

69,and\JQ .withstationar.y contacts 62andfl2,

respectively, for, .controlling the .hoist.rnotor. soVv as tooperate in thelowering direction.

The-. control.. device CO `is preferably designedA mythe-form vof a customary master'controller.,

whilethe-reversing. switclnRS. and .its contacts...

are..preferably electromagnetic conta-ctors. which are f controlled in; accordance. with. .the selected hoistingpr; loweringposition' of .the masterv oontroller., Since the particular designof .the operator-actuated control elements, .here .represented by CO and RS, is not essential for the-invention properland, aS-suCh, neednotinvolve novelty over the `,mastercontrollers; the lsimplified illustration inFigg 1 .hasfbeenchosenfor the `sakecf Acone,V

venience .and clarity.: v

The armature-29V f of tthe mainsgenerator and fthegarmaturef 30 of 4,the control ,generator CG arefmountedfon -a--coinmnn shaft 3 which, when in operation-Vis drivengby aconstantfspeed motorV M1. Satisfactory operation can also be obtained if armature 30 lis drivenfat constant speed'while armature f2!) is actuated by separate drive.' means whose speedsdocs` notwary excessively.

Field winding 33 ofy the, control generator CG is energized. byga regulator. :circuit AA3 which; is f connected `towthe-` armature -Mlfoi" a regulating generator RG through an adjusting rheostat R6 for varying the resistance of the regulator armature circuit A3. The calibration of rheostat R6 need not be changed during the operation of the control system.

Armature 4|) of regulating generator RG is mounted on a common shaft 5 with armature 50 of the above-mentioned exciter EX. Shaft 5 is connected to a constant speed motor M2. It will be understood, however, that the illustrated arrangement can be modified by using a single constant speed motor for the operation of both shafts 3 and 5, or by connecting the two shafts 3 and 5 with each other so as to obtain a single motor driven generator unit.

The regulating generator RG has three field windings 4|, 44, 45. Field winding 4| corresponds to the pattern eld winding 3| of the control generator CG and is connected in series with this winding so as to be energized by the pattern voltage adjusted at the controller CO. Field winding 44 of regulating generator RG is similar in function to the voltage or speed responsive eld winding 34 of control generator CG and is connected in series therewith across armature of main generator MG, a calibrating resistor R4 being inserted in series with winding 44. Field Winding 45, hereinafter called the regulating field winding, is excited in accordance with the current in the feed circuit AI and to this end is connected, through a Calibrating rheostat R5 and leads 23 and 25, across a voltage measuring impedance in circuit AI, for instance the interpole and compensating winding 22 of generator MG in parallel to the IR-drop compensating field winding of generator CG. When in operation, both windings 35 and 45 are traversed by a current whose magnitude varies in accordance with the voltage drop across the interpole field winding 22.

In order to achieve the control functions in accordance with the above-stated objects of my invention, a particular design of the two auxiliary generators CG and RG and their appertaining field exciting means is necessary, as will be set forth presently.

The control generator CG is a small electric generator, similar in design to conventional exciters. Like exciters, it possesses the ability to accurately amplify small amounts of energy supplied to its field into larger amounts for the control of large electrical machines. However, the control generator possesses this ability to a much higher degree and represents a sensitive amplifier, capable of working on very small inputs to its fields to produce a very large output in the armature circuit. This sensitivity is due to the action of the self-excited field winding 32 which feeds a. small portion of the control generator output power back into the control generator as excitation to produce still more output. The field of winding 32 is just sufficient to sustain the generated voltage but, by itself, is incapable of building up the output of the machine. Hence the action of the control generator is always under the control of one or more of the separately excited fleld windings 3|, 33, 34 and 35.

With this adjustment of the self-excited field, the ampere turns from the other eld exciting means (windings 3|, 33, 34, 35) can be balanced to the null point. This null condition exists when a field excitation which measures the motor speed is balanced by the field excitation of the pattern field winding caused by the standard or pattern voltage as adjusted, at will, by the operator by selecting the position of the master controller.

The motor speed corresponds to the fundamental equation:

SpeedzconstantX (applied armature voltage-armature IR drop) As stated previously, the voltage responsive field winding 34 of generator CG measures the armature voltage, and the winding 35 measures the interpole IR drop which is proportional to the motor armature IR drop since winding 22 carries the same current as the motor armature. The relative polarities of iield windings 34 and 35 are such that their ampere turns are subtractive `differential relative to each other and thus satisfy the above equation. The resultant speed measuring ampere turns of windings 35 and 34, as a whole, are balanced against the pattern field of winding 3|.

When the motor is running at the speed called for by any selected setting of the master controller, the speed measuring ampere turns exactly cancel the ampere turns of the pattern field. Assuming the current limiting eld winding 33 to be deenergized at this moment, the only effective excitation on the control generator comes now from the field of the self-energized winding 32 and there is no tendency to change the generator excitation. Should the motor speed vary from the proper value, the balance between the pattern and speed measuring excitations is disturbed, the resulting excess ampere turns then act to correct the error in motor speed, In this manner the control generator CG provides a sensitive and accurate speed regulation. However, it has also a current or torque limiting effect due to its interconnection with the regulating generator RG.

It will be seen from the foregoing description that the control fields on the control generator that is the pattern, voltage and IR-drop fields, have their counterpart on the regulating generator and that the corresponding field windings of the two auxiliary generators are connected in series, with the exception of the current and IR-drop field windings 35 and 45 which are paralleled to provide for independent adjustment. The proportions and relative polarities of the control fields and the current limiting eld of the control generator CG are such that the current limit field will cancel the effect of any of the control fields under given operating conditions to be explained later. In other words, suppose there is a current of one ampere in the pattern field winding 3| on the control generator. This current also flows in the pattern field winding 4| of the regulating generator and generates the proper voltage to make the ampere turns of the current limit winding 33 oppose the ampere turns of the pattern eld winding 3|, when this is necessary to limit the load current of motor HM.

In order to apply such a current limiting control, some means must be employed to produce this canceling action only at times when the load current would otherwise exceed a safe maximum value. To accomplish this, the regulating generator RG is given the special characteristic typified by the curve in Fig. 2. This characteristic differs from that of conventional machines by having an extended low-voltage or zerovoltage interval between points F and P which are both displaced from the zero point O by fixed amounts of excitation.

amamos y7 A.Afcharacteristic: of: this itypel can ibeezobtained by providing the field poles of the generatorwith a :saturable magnetic shunt :as exemplified' "by Fig. 3 and Fig. 4.

It is essential for the invention that the regulating generator RG'orthe appertaining circuit connections include a saturable magnetic device for producing a current-limiting control effect. This Will'be explained hereinafter. For. the sake of convenience, however, a more complete description ofthe remaining electric circuit devices shown in Fig. l may first be given.

The exciter iL-XV has tWoself-exciting fields 5l and 52. V5I is a shunt field and connected with the exciter output. circuit over an adjusting rheostat R'Vserving to adjust the exciter voltage to a proper magnitude. Rheostat R8 is not actu-l ated during the control operation of theY system sothat the exciter output voltage remains yconstant. in the exciter outputcircuit. A single exciter field Winding or a different arrangement and connection of the exciter field windings may be chosen Without affectingv the essentiai operation of the system sincetheonly'purpose of the exciter EX is to-represent a convenient current source of sufficiently constant voltage.

The control device CO here illustrated as a tapped resistor is preferably designed in the Aform of a customary controller, `and the reversing switch RS as a customary master switch. Since this preferable design of the main control elements is not essential for the invention proper, and controllers With master switches being Well known'as such, the simplied' illustration in-Fig. 1 has been chosen for the sake of convenience and clarity.

Turning now to a more detailed description oi the regulating generator RG,`let us recall the above-nentioned current-limiting function assigned to the regulating generator. As explained, the illustrated control system functions so as to operate the hoist motor HM in accordance with the direction and speed magnitude adjusted by the control device CO and the reversing switch RS. Suppose, however, that the slide contact |31 is displaced with such a speed in thedirection to cause motor HM to accelerate that the load current in circuit A! would exceed a safe value, thus overstressing the mechanical hoisting equipment and tending to cause excess sparking at the cominutator of the motor. Then the control effect of the regulating generator RG is of such nature as to'prevent these excess currents and accompanying detrimental phenomena. This limiting function is based on the fact that the excitation of the current-measuringr winding produces a eld cumulative to that of the principal field Winding di. Thus causing the excitation of'RG to be `greater than the point P in Fig. 2 which results in an output voltage and consequent-excitation of eld 33 on control generator CG. Field 33 opposes eld 3| and by thus controlling the excitation of CG and consequently the-main generator MG, the current in circuit, Al is limited tot the predetermined maximum value. That is, the intended effect of the regulating generator RG is to reduce the resultant excitation of the control vgenerator CG and hence the excitation ci the main generator MG and thereby the current and voltage magnitudes in the feed circuit Ai: `Of' course, thisreduction is only desired when the lo-adcurrent in feed vcircuit AI tendsv to exceedthe safe value.

t should be noted that should .the slider.I |.3'l .be

rIhe exciter eld 52 is series connected 8 movedrtodrapidlyftoward the high resistanceposition, the .inertiaf of theurevolving mechanical parts; including thesarmature of motor; HM can preventithe'hoist.fromifsloWingidoWn rapidly, and.

large regenerative currents may thenibe lpassed through. the feed lcircuit AI. The regulating generator RG thenxactsso as to make the field of winding 45 cumulative Withithat of Winding lil thus causing the. excitationof RGzto be greater than point F in Fig. .2. This excitationthenproduces an output' voltage which excites field33i ofV control generator CG in such direction as' to oppose winding-34. 'In this manner'it causes the output ofCG'to be maintained at such'val'ue that the main generator MG voltage is maintained at such a value that the regenerativeL current of motor HM is limited to the predetermined maximum value.

An ideal method of Vobtaining the just-'meritioned load limitation by the action of the'regulating generator R'Gvvould. be tokeep the current through eld winding-133' zeroV fori all permissible values of current in the feed circuit Al but' to cause this field current to rise sharply from zero to a relatively high value vfor=1any current inexcess of the maximum permissible value. In order to have the regulating generator RG produce such a control eiect, its magnetic saturation curve in the just-mentioned ideal case should'be similar tovthat denoted by the curv'ec in Fig.A 2.

vIn the coordinate system of Fig. 2, the abscissa represents values of excitation'felective yin the regulator armature RG-,-Whi1e the ordinateshoivs the voltage values in the regulator armature circuit 'A3, i. e. thevoltage effective'across the diiferential iield Winding `33 of the control gerierator CG.

According to this idealfsaturation curve v, the armature output lvoltage of ,generator vRG remains zero for all values ofexcitationupito'a. maximum value which' corresponds `to the desired maximumyalue of the current in the feedcircuit AI. Any excitation beyond that corresponding to the desired maximum value of current in circuit Al causes the voltage in circuit A3 to rise steeply to a much higher valuazthereby causing the differential field Winding 33 toA decrease the resultant field in generatorCG and hence the output voltage of the main genera-tor MG accordingly.

In order to achieve the ideal saturation curve just discussed, a, special magnetizable magnetic circuit is associated with alternate pairs of the poles of opposite'polarity of the energizing circuit oi the regulating generator RG. More particularly, the desired magnetic saturation effect is obtained by providing the magnetic field poles of the regulating generator with a magnetic shunt path so arranged and related to the main portion of the field pole that all of the magnetic flux is `bypassed away from the armature'as long as the shunt portion is unsaturated.

A generatorV for regulating purposes of the'type just suggestedis illustrated in Figs. 3 and 4. In

these figures, 4` designates the regulating'generator frame. This frame `4` carries 4the main or' exciting polesff', l, 8, and 9, and the interpoles 9. rhe poles 6 and 1 at their facing regions adjacent the armature 40 are provided with the projections I6 and I1 respectively. The poles 8 and 9 are provided with similar facing projections I8 and I9,

The magnetic shunt I4 is provided with an enlargement 26 disposed in cooperative relation to projection I6 and an enlargement 21 disposed in cooperative relation to the projection I1. The magnetic shunt I5 has the enlargements 28 and 29 disposed in cooperative relation to the projections I 8 and I9, respectively.

The poles 6, 1, 8, and 9 are rigidly secured to the frame 4 by the brass bolts 25 shown. A suitable number of brass shims 36 are placed between each of the poles and frame so that the radial air gap A is of a selected uniform value over each of the pole faces. The air gaps C formed at the places where the brass shims 36 are used are also substantially uniform in dimension radially since the pole pieces are assembled by the use of laminations of the same stamping, that is, the same dimensions.

The magnetic shunts I4 and I5 are secured to the frame 3 by means of brass bolts 31 and 38. Relatively thick brass blocks 46, 41, 48, and 49 are disposed between the enlargements 26, 21, 28, and 29, respectively, and the frame 4 in such manner that the air gaps B are of relatively large selected uniform width.

The magnetic shunts I4 and I5 are so dimensloned that their respective transverse sectional areas are considerably less than the transverse sectional areas of the respective poles 6, 1, 8, and 9. The poles 6, 1, 8, and 9 carry the field windings 4I, 44 and 45 and the shunts I4 and I5 carry energizing coils 4I', 44' and 45 connected in series, respectively, with the iield windings 4I, 44 and 45. The regulating generator has a commutating eld 32" connected in series with the armature.

Fig. 4 shows the direction of the fluxes in the regulating generator embodying our invention. The elds are represented by a single winding. In fact, for some types of control only one eld control winding may be used.

The novel results of our invention will now be clearer when the ux changes in the magnetic circuits of the regulating generator RG, as indicated in Fig. 4, are considered in detail. For all permissible variations in load current of motor HM, the flux paths are as follows:

For poles 6 and 1, the flux is from the frame 4 through the root portion of the pole, the projection I6, enlargement 26, magnetic shunt I4, enlargement 21, projection I1, and the root portion of pole 1 back to the frame. For the other pair of poles 8 and 9, the flux is from frame 4 through the root portion of pole 8, projection I8, enlargement 28, magnetic shunt I5, enlargement 29, projection I9, the root portion of pole 9 back to the frame.

From these two paths just traced, it is apparent that no iiux is provided across air gap A; and, in consequence, there is no voltage generated by the regulating generator RG as long as the load variation on motor HM is within the desired range.

As soon as the load exceeds the desired or safe value, the magnetic shunts I4 and I5 saturate and almost instantly, the regulating generator voltage begins to build up from point P along curve v to some higher value.

Since the output voltage of the regulating generator is supplied to neld 33 of the control generator CG, it is apparent that the voltage of this control generator drops on sharply with the result that the voltage supplied to motor HM from the main generator MG is sharply reduced. The novel and special construction of our regulating generator thus provides a control voltage characteristic that stays at zero from the origin@ to point P and then rises from point P along the solid curve v.

By prior attempts, the ideal or theoretical curve v could not be attained. At best, a characteristic somewhat like curve v could be obtained. By proper selection of the air gaps at A, B, and C, and the dimensioning of the magnetic shunts I4 and I5 in proper relation to the main poles, not only can we obtain a curve such as 'LJ-which is for the usual constant current regulating requirements the idealbut we may obtain any curve from v to v.

Further, by the use and disposition of the shunts I4 and I5 as indicated, ample space is provided for the commutating poles I2 and I3. The use of commutating poles allows for the armature load to be increased to the full current rating. The rotating regulator or regulating generator RG is thus able to commutate the same loads as an ordinary direct-current generator using the same armature.

W'hat makes the regulating generator so effective and sensitive is the fact that the resistance of the self energizing eld 32 coincides with the straight part or air-gap portion of the saturation curve. In our particular showing, it will be apparent that curve v is parallel to the air-gap line and thus is as effective as if curve v, at the sloping portion, were superimposed on the airgap line.

While we have sho-wn and described but one special construction of the amplifying regulating generator and have illustrated but one applica.- tion, it is apparent that others, particularly after having had the benet of our teaching, may devise regulating generators for accomplishing the same or similar results. We, therefore, do not wish t0 be limited to the particular showing made, but Wish to be limited only to the scope of the claims hereto appended.

We claim as our invention:

1. In a direct-current generator, in combina-V tion, a magnetic frame, a plurality of pairs of poles on the frame, a magnetic shunt having a lesser transverse sectional area than the poles disposed to shunt the magnetic ilux of alternate pairs of poles of opposite polarity, an armature and windings on said armature iield windings on the poles for producing a flux through said armature in one sense, coils connected in series with the iield windings disposed on the shunts wound to produce a iiux through said armature in an opposite sense, means for exciting said iield windings and coils with a current that varies from zero to some selected relatively high value, whereby the Voltage output of the generator armature is substantially zero for all values of currents in said iield windings and coils of a value too small to saturate the magnetic shunts.

2. In a direct-current generator, in combination, a frame, a pair of pole pieces mounted in circumferentially spaced relation on the frame, an armature, a magnetic shunt magnetically connected to the toe of one pole and the heel of the other, said magnetic shunt having a much lesser transverse sectional area than the poles, means for exciting the poles with opposite polarity by a 4variable magnetiaingfforce, and means piece, a magnetic shunt disposed across .the out- A ward surfaces of the projections, means for lexciting said shunt, an armature, vsaid magnetic shunt being selected in dimensions and excitation characteristics to saturate at a much lesser magnetizing force than required for saturation of the pole pieces, and means for magnetizing said pole pieces with opposite polarity, and in an opposite sense with respect tothe karmature than the excitation of said shunts v vith respect to the armature, by a magnetizing force that may -vary'irom zero to a force-sufficient to saturate the pole pieces.

4; In-a directtcurrent generator, in combination, a frame, an armature, four pole pieces secured to the frame at substantially equally spaced points -on the frame, a projectionlatrthe heel oreachrof two diametrically oppositelpoles, a similar projection at the. toe of each of the other tvvodiametrically opposite poles, a magnetic bridge disposed over eachlof .the two facingprojections, and means for magnetizing the pole pieces and the magneticbridges by amagnetizing force that may vary from zero to a given maximum, said magnetic bridges being dimensioned to become saturated at a magnetizing-force. considerably less than said given maximum, the `direction of the'magnetization in each of said bridges being Such that themagnetomotiveforce produced thereby in thek armature is in an opposite sense tothe magnetomotive force produced in the armature by the magnetization of;v the pole pieces.

5. In a direct-current generator, in combination, a frame, an armatura four pole pieces secured to the .frame at substantially equally spacedpoints onlthe frame, a projection ,atv the heel'of each of two diametrically opposite poles, a similar projection at the toe oieachof the other two diametrically opposite poles, a magnetic bridge disposed over each of the two facing .projections, commutating poles disposed'between the pole pieces at each ofthe facing regions ofthe pole pieces having no projections, and means for magnetizing the, pole pieces and the magnetic bridges by a magnetizing force thatk may vary from zero to a given maximum, said magnetic bridges being dimensioned tov become saturated at a magnetizing force considerably less than said given maximum, andthe direction ofthe magnjetization in said bridges being such that` the magnetomotive force. produced in the armature is in an opposite senseto the magnetomotive force produced in the arma-ture by the magnetization of the pole pieces.

6. In a direct-current regulating generator, in combination, aframe,an armature, and an even number ci pole pieces secured to the frame, a

projection on the toe of every odd-numbered pole piece, a projection on the heelof every evennurnbered pole piece, aA magnetic shunt mag.,-

ijlcient .to saturate .the pole Y pieces ,proportional to the magnetizing-iorce inthe magnetic s huntand in a direction to producegafmagnetomotivefierce i'nxthe armature inc-.anotherfdirectiom whereby the magnetization-citric armature remains at Ybelow.-Zotoffor @nevrotico-of risoin magnetisme force and rises proportional to -Athe magnetizing force forstill larger rises 01".mag-neti-zing force.

7. In a direct-Current regulating-generator, in combination, a .ira-me, an armature, and an even numborof polo-pieoosfmountodat-equally spaced Qoi'otsori the inno-r-Suriaoo .oflthe iframe, `erf-rolatively thiol;` projection at the heel of every oddnumbered pole piece, aesiinilarfprojectionat the toe .of .every even-,numbered Ypole piece,- eachpair of facing; projections havingcoplananflat sur.- fraces Yatythe' reg-ions .remote from the-armature, magnetic -`S1o1mtsfy o f-oor1idorab1yf .lossercrosssection than thefpolepieces, disposed -across-ethe flat surfaces of eachipairof facing projections, and means for proportionally magnetizingi'the polepiecesfand Shu-.nts by `a-magnetizing; force that 'morbo vorioti trom- =zorotosuoh .vaiuevas to `saturate the'pole-pieces, thedirectionV ofthe magnetization ofthe shunts :boineso ,chosen ,that themagnetizing eirect'infthe armature-is opposite to. the inocuo.tizitieY ofieot the Y armature produced-bythe 4flotter,.iotitotion ofthe pole pieces.

8'- In-afiiirect-oorrotit regulating. generator; .in oombinationf otranto, on armature-fand on even Y11i-unifieroit-polo rioooomountodot oooallyispaood points on the inner surface of the frameanclatively thick;VY projection .t at: the .heel of everyv o ddnumbered pole piooefotimiiarprojection at the toe of. every evenenumbe-red-.pole piece, 4each -pair offacing l proiootions having oonianofr: flot S11-,rfaces at Vthe regions rernoteromfthearmature, magnetic, shunts, or ,considerably lesser .i crossesection-thonthe polo-pieces, disposed across thefat surfaces of-eachpairofifaoinaproieotionafoom- ;mutetingf, polos.- disposed irieooh of. the rv spaces between the pole pieces-not ooouniodbvptoioof tions, and mean5- forproportionally magnetizing the-pole pieces andfstiutltsl by a maenotizirie. .force that m2o'j be rariedffrom Zoro tof o value to ,saturate the poloioiooos the direction ofthemaenetizationof the .shunts being, so chosen as to kproducea magnetomotivaforce linsaid armature opposite .to themagnetomotive-force produced 1in the armatureby the magnetizationof the. Dole pieces.

oem combination;amat-magneti@.oitouithavt ing an air gap therein, a parallel magnetic-member shunting said7 air gap. and ,of lesser lcrosssectional area thangsaid,first,magnetic. circuit, excitation .means ion-Said. first .magnetic circuit, excitation meansorsaidfparallel :magnet/ic,mem` bor Shooting Said ait son, moansx for-.Simultaneously energizing both of said excitation means, the Winding.V relation of Scifi two.y excitation means` being; 4such as to, produce` opposing mag,- netomotive forcesacross saidfair gap, and magnetic flux responsive means` disposedv in saidair gap to be linked'b'ythe magnetic'vuxthereacross.

1,0. In an electricv potentialproducing, device, in combination, a magnetic circuitlincluding'; a

ymain part, a secondary part including means having circuits for producing an electrical potential, and a magnetic shunt across said secondary part, said shunt having a section such that it becomes saturated more readily than said main part and secondary part, means for exciting the main part in such manner to produce a magnetomotive force from left to right in the secondary part and left to right in said shunt, and means for exciting the shunt in such manner to produce a magnetomotive force from right to left in the secondary part but from left to right in said shunt, whereby the electrical potential produced may be caused to vary, with a proportional variation of the excitation of the main part and shunt from zero to a value sufficient to saturate the main part, 'from zeroto a given relatively low Ypotential value for a variation of the excitation from zero to a given value, and from said given relatively low potential value to a relatively high positive potential value for a variation of the excitation from said given value to a value sufficient to saturate the main part,

11. In an electric potential producing device,

in combination, a magnetic circuit including, a .Y

main part having a relatively large sectional area, a secondary part including rotatable armature means having circuits for producing an electrical potential and having a sectional area substantially equal to the sectional area of the main part, and a magnetic shunt across said secondary part, said shunt having a section such that it becomes saturated more readily than said main part and secondary part, means for exciting the main part in such manner to produce a magnetomotive force from left to right in the secondary part and left to right in said shunt, and means for exciting the shunt in such manner to produce a magnetomotive force from right to left in the secondary part but from left to right in said shunt, whereby the electrical potential produced may be caused to vary, with a proportional variation of the excitation of the main part and shunt from zero to a value suiiicient to saturate the main part, from zero to a given relatively low potential value for a variation of the excitation from zero to a given value, and from said given relatively low potential value to a relatively high positive potential value for a variation of the excitation from said given value to a value sufficient to saturate the main part.

l2. A dynamo-.electric machine for regulation, in combination, a direct-current generator having an armature, or rotor, and windings thereon, a magnetic circuit for providing a ux through the armature in one sense, said circuit including a frame member, two poles and the armature, the frame member being separated from the outer ends of the poles by relatively large air gaps, a second magnetic circuit for providing a ilux through the armature in another sense, said second 'magnetic circuit including a second frame, the same two poles, and the armature, said second frame being of much lesser sectional area than the iirst magnetic circuit, first eld windings for producing a flux in the rst magnetic circuit, means for varying the excitation current of the rst eld windings from zero to saturation of the first magnetic circuit, second eld windings for producing a ilux in the second magnetic circuit, means for varying the excitation current of the second `Field windings from zero to saturation of the restricted sectional portion of the second magnetic circuit, the winding direction and current direction in the second eld windings being such that the magnetomotive force across the armature is in opposition to the magnetomotive force produced across the armature by the current in the rst field windings.

13. A dynamo-electric machine for regulation, in combination, a direct-current generator having an armature, or rotor, and windings thereon, a magnetic circuit for providing a iiux through the armature in one sense, said circuit including a frame member, two poles and the armature, the frame member being separated from the outer ends of the poles by relatively large air gaps, a second magnetic circuit for providing a flux through the armature in another sense, said second magnetic circuit including a second frame, the same two poles, and the armature, said second frame being of much lesser sectional area than the iirst magnetic circuit, rst iield windings for producing a iiux in the rst magnetic circuit, second eld windings for producing a flux in the second magnetic circuit, means for varying the excitation current in the second iield windings from zero to saturation of the restricted sectional portion of the second magnetic circuit, the winding direction and current direction in the second field windings being such that the magnetomotive force across the armature is in opposition to the magnetomotive force produced across the armature by the current in the first field windings.

14. A dynamo-electric machine for regulation, in combination, a direct-current generator having an armature, or rotor, and windings thereon, a magnetic circuit for providing a iiux through the armature in one sense, said circuit including a frame member, two poles and the armature, the frame member being separated from the outer ends of the poles by relatively large air gaps, a second magnetic circuit for providing a iiux through the armature in another sense, said second magnetic circuit including a second frame, the same two poles, and the armature, said second frame being of much lesser sectional area than the first magnetic circuit, rst field windings for producing a fluX in the first magnetic circuit, second eld windings for producing a flux in the second magnetic circuit, the winding direction and current direction in the second iield windings being such that the magnetomotive force across the armature is in opposition to the magnetomotive force produced across the armature by the currentin the first field winding.

15. A dynamo-electric machine for regulation, in combination, a direct-current generator having an armature, or rotor, and windings thereon for producing a voltage output, and having three magnetic circuits, the rst circuit including a frame member, two poles and the armature, the frame member being separated at the ends remote from the armature by relatively large air gaps, the second magnetic circuit including a second frame member, the same two poles, and the armature, the second frame member having low reluctance connections with the poles at points remote from the armature and having a sectional area considerably less than the rst magnetic circuit, whereby the second frame member will normally saturate considerably sooner than the first magnetic circuit, and the third magnetic circuit including the two frame members, winding means on the nrst frame member, and winding means on the second frame member, the winding relation and the direction of the current normally in use being such that the magnetomotive forces produced by the curalmenos' rents/3 their windings; isf: additive in the third magnettcfcircuit., i

:16. dynamo f'eiectric. machine i for regulation, in combination, a directecurrentgenerator havngiganyarmature; .or.. rotor; and `windings .thereon for producing `:a zvoitagewontput; .and having three .magnetica circuits;- thexzfrrst ycircuit':includingi :a frameztmember, two :poles and-the armature,V the frame,L member being-f separated; ati-the.; ends cre.- moteefrom fthe armature by :relatively #large air gapsfitherfrsecondz magnetici circuiti including;A4 a secondzframei-memben tiie'zsame two po1es;and the-2 armature, .thefsecondsjrame ,member having low,-v .ieiuctazncegconnections With the' poles: at

pointsv remotes from- .thee armaturev and" having: a

sectonale: area considerably less than' the: Erst rrragnetic"l circuit, :whereby: the Asecond* frame membervv will normally saturate considerably sooner''than the: rst magnetic circuit, and -the magnetic,` circuit includingY theA -tWo frame 156 members-,zwindingmeans Von thefrst frameber;. Winding` means; vconnected' inzfseriesxwith thezrst windingfmeans;v Vdisposed'.on theisecond frame member,v the winding: direction; being'. so .chosen thatpwhen .currentttraverses :the :winding means. thez magnctomotivev forces 1 produced; in the .third magnetic vcircuit Willlberadditive.

ALBERT. KIIMBALL. AMAR'IfIN-iH;

REFERENCESz'CITEDy The vfoHowing references are' ofrecordn 'the iieaof thisP` patenti:

UNITEDY- STATES.' .PATENTS Nmnkicr: lName Date 2,058,339.- Metzgerf Oct.20, ,1936 2,264,272 Blankenbuehleret` a1. Y Dec.' 2;, ,1941 2,37 8,894 Blankenbulehlei; v June 26,. 1945 $2,383,971y IVY; Sept. 4, 1945 

